Simple Automatic Night Lamp Circuit using Battery Power

A Simple Automatic Night Lamp Circuit that runs on batteries is a simple and energy saving lighting system.

It turns on when it gets dark and turns off when it is light outside.

This kind of lamp is really useful in places like bedrooms, hallways and stairs because it provides light when you need it at night.

The power for this lamp comes from two 1.5V batteries connected together.

The design includes a low power 7555 timer chip a light dependent resistor LDR and a light emitting diode LED that gives off the light.

Circuit Working:

Parts List:

Here the diagram shows how a low power LED night lamp is designed to turn off when it is light outside.

The key part of this circuit is the light dependent resistor LDR R4, which changes its resistance based on how much light is around.

When it is bright during the day the LDRs resistance goes down a lot which keeps the whole circuit turned OFF.

But when it gets dark the LDRs resistance goes up which turns on the IC 7555 timer making the LED light up.

The 7555 timer acts like a switch and it works with a setup of resistors R1, R2 and the LDR R4 that create a voltage divider.

If the voltage at pin 2 called the trigger pin drops below one third of the total supply voltage the output at pin 3 goes HIGH turning the LED1 ON.

Capacitor C1 which is 100nF helps keep the timer working well.

Capacitor C2 with a value of 220µF acts as a filter to make sure the circuit runs smoothly.

To make the circuit even more reliable the 1N5819 Schottky diode is included to stop any reverse current, ensuring it works well even with a low voltage of 3V.

Formulas with Calculations:

The formulas with calculations for Simple Automatic Night Lamp Circuit using Battery Power is mentioned below:

LDR Resistance Calculation:

The LDR resistance varies with light intensity.

The approximate resistance values are:

Bright Light: 1k

Darkness: 1M

The voltage at Pin 2 Trigger Pin of IC 7555 is given by the voltage divider equation:

Vtrigger ​= Vcc ​× R4​ / (R1 + R4)

For the 7555 to turn ON the LED V_trigger must be below 1V.

RC Timing Calculation:

The time delay (if needed) can be estimated using the standard 555 timer formula:

T = 1.1 × R × C

where

R = 47k (R3) and C = 220µF (C2)

T = 1.1 x 47000 x 0.00022 = 11.374 seconds

How to Build:

To build a Simple Automatic Night Lamp Circuit using Battery Power following the below mentioned steps:

• Gather all the components as mentioned in the above circuit diagram.
• Connect pin 1 of IC1 7555 to GND.
• Connect pin 2 of IC1 to pin 6 of IC1.
• Connect pin 3 of IC1 to positive of capacitor C2 and connect the negative of capacitor C2 between cathode of LED1 and anode of D1 diode.
• Connect pin 4 of IC1 to positive supply through resistor R3
• Connect a resistor R2 between pin 6 and pin 7 of IC1 7555.
• Connect a resistor R1 between pin 7 and positive supply.
• Connect a LDR R4 from pin 4 and GND.
• Connect a capacitor C1 from pin 2 of IC1 and GND.
• Connect pin 8 of IC1 to positive supply of 3V battery.
• Connect the positive supply of circuit to +3V of battery and GND to (-) negative supply of the 3V battery

Conclusion:

This Simple Automatic Night Lamp Circuit using Battery Power is an easy to use and efficient low power device.

It turns ON by itself when it gets dark and turns OFF when there is light which helps save energy.

The IC 7555 timer helps it work smoothly while using very little power making it perfect for battery

powered use.

You can change the light sensitivity by adjusting the LDR and resistor values so it can work well in different settings.

References:

LDR Based Automatic night lamp